A place to discuss the ecology and evolution of plants as well as the functioning of ecosystems.
Companion to Resource Strategies of Wild Plants, Princeton University Press.

Tuesday, December 17, 2013

Greenhouse gas emissions from livestock

A follow-up to FAO’s Livestock’s
long shadow, a new document from the FAO revisits the contribution of the
livestock sector to global GHG emissions. LLS had stated that 18% of GHG
emissions could be attributed to livestock. Here they examine patterns of GHG
emissions more carefully.

A couple of interesting points in the document.

First, there is a good summary of the drivers of our
livestock systems have changed:

“Traditionally, livestock was supply driven, converting
waste material and other resources of limited alternative use into edible products
and other goods and services. Its size was relatively limited and so were the
environmental impacts. However, since the livestock sector has become
increasingly demand-driven, growth has been faster and the sector now competes for
natural resources with other sectors.”

In short, cattle use to graze marginal lands. Pigs were fed
scraps. Now they compete with people for food.

They also have good summaries of the intensities of
emissions at the global scale. Industrial agricultural is often thought to be
intensive, but their efficiencies can be high.

The authors state that “High intensity of emissions are
caused by low feed digestibility, poorer animal husbandry, and higher ages at
slaughter. When feed digestibility is high and animals are brought to market
quicker, intensity of emissions can be lower. Hence, industrial production of
livestock tends to be associated with low intensity of emissions per unit
protein produced. “

In short, when using marginal resources, efficiencies are
lower. Graze animals on low-protein grass, and they gain weight slower and release more methane.

Still, the authors do not pull apart the relative
contributions of different components of the supply chain. For example, what is
the relative efficiency of grazing in North America vs. feeding cattle grain?
Almost half of the emissions with cattle production come from feed production
and processing.

The document also provides recommendations for reducing GHG
emissions. Mostly, they say use “first-world” practices everywhere. The
first-world systems are left with managing their manure better.

No mention of
producing or demanding less meat, or relying less on grain, as a mitigation strategy as far as I read.